Distinguishing Low and High Water Consumers—A Paradigm of Disease Risk

Abstract

A long-standing body of clinical observations associates low 24-h total water intake (TWI = water + beverages + food moisture) with acute renal disorders such as kidney stones and urinary tract infections. These findings prompted observational studies and experimental interventions comparing habitual low volume (LOW) and high volume (HIGH) drinkers. Investigators have learned that the TWI of LOW and HIGH differ by 1–2 L·d−1, their hematological values (e.g., plasma osmolality, plasma sodium) are similar and lie within the laboratory reference ranges of healthy adults and both groups appear to successfully maintain water-electrolyte homeostasis. However, LOW differs from HIGH in urinary biomarkers (e.g., reduced urine volume and increased osmolality or specific gravity), as well as higher plasma concentrations of arginine vasopressin (AVP) and cortisol. Further, evidence suggests that both a low daily TWI and/or elevated plasma AVP influence the development and progression of metabolic syndrome, diabetes, obesity, chronic kidney disease, hypertension and cardiovascular disease. Based on these studies, we propose a theory of increased disease risk in LOW that involves chronic release of fluid-electrolyte (i.e., AVP) and stress (i.e., cortisol) hormones. This narrative review describes small but important differences between LOW and HIGH, advises future investigations and provides practical dietary recommendations for LOW that are intended to decrease their risk of chronic diseases.

Rehydration during Endurance Exercise: Challenges, Research, Options, Methods

“…If salt depletion is suspected (e.g., increased salt appetite or salt craving), it is prudent to consider adding specific dietary food items to ensure that daily sodium intake replaces exercise-induced sodium loss. Refer to [97] to identify the amount of sodium in common food items. Sodium supplementation during meals should be guided by dietary recommendations for daily sodium intake [127], and by considering the potential negative health effects of chronic high dietary salt intake [128].…”

“…However, as shown in Figure 5 , the P osm threshold at which thirst is perceived varies greatly across individuals (range, 274–293 mOsm/kg) and may be lower than the range of laboratory reference values for P osm (285–295 mOsm/kg) [ 96 ]. The data in Figure 5 were compiled from 5 published human studies; the shape of this frequency distribution implies that the thirst threshold is a multifactorial (polygenic) characteristic [ 97 ]. Although inter-individual differences of the P osm threshold for thirst have not been studied during exercise, Figure 5 suggests that the level of dehydration (i.e., increased P osm ) that initiates drinking during exercise might differ considerably among athletes.…”

“…Reprinted under the terms and conditions of the Creative Commons Attribution (CC BY) license ( ) accessed on 2 March 2021. Modified from [ 97 ].…”

Fluid Intake Recommendation Considering the Physiological Adaptations of Adults Over 65 Years: A Critical Review

“…In contrast, other researchers [51] have noted that the specific gravity, color, and osmolality of urine have been widely advocated for screening of dehydration in older adults and that, as a result, these measures should not be used to indicate hydration status in older people (either alone or as part of a wider tranche of tests). In a recent study, Armstrong et al [52] concluded that low volumes differed from high volumes in terms of urinary biomarkers (e.g., reduced urine volume and increased osmolality or specific gravity) and that a self-assessment of urine color provided useful feedback regarding excessive drinking.…”

Chronic Dehydration in Nursing Home Residents

“…Although some studies have reported no difference in serum osmolality between habitually low fluid intake and high fluid intake [ 13 ], even a slight increase in serum osmolality was found to stimulate the release of arginine vasopressin and cortisol, which are known to heighten the risk of chronic diseases. In clinically stable long-term care residents, elevations of serum osmolality were frequently observed without clinically overt signs of dehydration [ 14 ], so using serum osmolality to assess chronic dehydration is considered reasonable.…”